Thismia velaris Dančák, Sochor & Hroneš, 2025

Thismia velaris Dančák, Sochor & Hroneš , sp. nov. ( Fig. 1 View FIGURE 1 & 2 View FIGURE 2 )

Diagnosis:— Thismia velaris is externally similar to T. malayana but differs by floral tube colourless translucent between veins (vs. brown in the upper half), flat annulus (vs. outer margin of annulus prominently raised), having three triangular lobes on supraconnective apex (vs. five appendages of three different shapes and sizes), and the central part of the lateral appendage elongated into membranaceous veil exceeding the apices of the supraconnective lobes (vs. central part of the lateral appendage without the veil, not exceeding the apex of the supraconnective appendages).

Type:— MALAYSIA. Sarawak: Kuching Division, Kuching District, Semenggoh Nature Reserve, lowland mixed dipterocarp forest 700 m WSW from the main entrance, 73 m a.s.l., 1.3970089° N, 110.3192761° E, 31 January 2023, Dančák & Sochor BOR 30/23 ( holotype SAR! [in spirit]).

Description:—Achlorophyllous herb, ca. 5–6 cm tall. Roots creeping, vermiform, ± horizontal, sparsely branched, ca. 1 mm thick, pale brown. Stem 3.5–4.0 cm long, erect or ascending (to creeping), smooth, cream to pale brown, bearing 1 or 2 flowers. Leaves 4.5–5 × ca. 2 mm, spirally arranged, appressed, scale-like, narrowly triangular, acute, entire, of the same colour as stem. Bracts subtending each flower 3, similar to leaves, but 7–8 mm long. Flower subsessile, generally actinomorphic (except for floral tube), ca. 14–20 mm long. Floral tube 10–15 mm long, 8.3–9.0 mm wide, asymmetric; its shape ranging from ± cylindrical in the basal fifth, then conspicuously protuberant at one side, slightly narrowed at above the half and widest at the upper quarter to sixth, to the wider part of floral tube inclined at an angle to the narrow basal part and the ovary; outer surface ± smooth, colourless to whitish, sometimes with orange-brownish tinge in upper third, translucent, with 12 orange to brown longitudinal veins slightly protruding above the surface of the tube as low ribs; inner surface with colourless transverse bars. Annulus thin, flat, hardly raised above the top of floral tube, outer margin circular to hexagonal, inner margin circular, transparent-yellow in the outer part, inner part brightly yellow to orangish and forming more or less distinct hexagonal figure. Tepals 6, equal in shape and size, 4–7 mm long, ca. 3 mm wide at base, narrowly triangular with arcuately widened base, translucent-yellow, pale orange to brown with three basally widened orange to brown stripes, gradually converging towards the apex; filiform appendage arising from the abaxial side of tepal, 6–8 mm long (measured from the tepal tip), tubular, apically unswollen, orange-brown or brown to dark brown, lighter at the apex. Stamens 6, pendent from the top of floral tube; filaments arcuately curved in both transversal and longitudinal view, sponge-like, yellow; connectives flattened, laterally connate to form a tube; each connective 5.5 × 2.0 mm, rounded and yellow at base, colourless and transparent in the middle; supraconnectives free, somewhat tapering, trilobed, blue, translucent; lobes triangular; lateral lobes ca. 0.9–1.0 mm long and 0.5–0.7 mm wide at base; the middle lobe ca. 0.4 × 0.3 mm; lateral appendage with two shallowly bilobed lateral wings each bearing several hairs, the middle part rather flat and extended downwards in the form of thin bluish-translucent veil rectangular in outline with the apical margin irregularly dentate-hairy, usually exceeding the apex of supraconnective lobes; interstaminal gland inserted on the line of fusion between connectives, globose. Style 1.3–1.5 mm long, brown to dark reddish-brown; stigma 3-lobed, lobes 1.3–1.4 mm long, bifid to ca. 1/4 of its length, papillate, very dark brown. Ovary inferior, ca. 3.5 × 3–4 mm, obconical, slightly verrucose, pale brown, darker on top. Fruit an obconical orangish capsule (ripe fruit not seen). Seeds not seen.

Additional field records: — MALAYSIA. Sarawak: Kuching Division, Kuching District, Bako National Park [without precise locality], 22 February 2011, photo Katarina Stenman (www.inaturalist.org/observations/102264309) ; Semenggoh Nature Reserve , lowland mixed dipterocarp forest 700 m WSW from the main entrance, 73 m a.s.l., 1.3970089° N, 110.3192761° E, 1 February 2024, photo M. Hroneš & A. Uvírová GoogleMaps .

Habitat: —The type population was found in a lowland mixed dipterocarp forest on a gentle slope with several shallow longitudinal depressions near a small running stream, indicating moderate humidity and a well-developed humus layer. Habitat at the second locality is not known.

Distribution: — Thismia velaris is known from two localities in western Sarawak. In addition to the type locality in Semenggoh Nature Reserve, a single individual was observed in Bako National Park.

Conservation status: —While the extent of occurrence (EOO) of T. velaris cannot be calculated from two points, the area of occupancy (AOO) is formally estimated at 8 km 2. Both known populations occur within protected areas (a nature reserve and a national park), and no population decline can be inferred or projected. However, the number of currently known individuals is markedly less than 50, and T. velaris is therefore preliminarily assigned a IUCN Red List status CR (D) according to the guidelines of the IUCN Standards and Petitions Subcommittee (2025).

Etymology: —The specific epithet is derived from the Latin word velum (veil, curtain), referring to the unique veil-like structure hanging from the lateral appendage of the stamen.

Notes: —Besides its distinctive colouration ( Fig. 1 View FIGURE 1 ), Thismia velaris is notable for the protruding to ventricose wall of its floral tube, a feature more closely resembling the unrelated Neotropical T. panamensis ( Standley 1927: 163) Jonker (1938: 234) than the Old World congeners. Although some of the Old World Thismia species can be described as having zygomorphic floral tube, e.g. T. abei ( Akasawa 1950: 193) Hatusima (1976: 7) , T. cornuta Hroneš, Sochor & Dančák in Hroneš et al. (2018: 111) and T. pappilata Nuraliev & Yudina in Nuraliev et al. (2024: 262), their tube is either simply bent or bent and displaced from the ovary axis. On the other hand, the floral tube of T. velaris is typically cylindrical in its basal fifth, conspicuously protuberant on one side, slightly narrowed above the midpoint, and widest in the upper quarter to sixth.

Among the Old World species of Thismia , T. velaris shows considerable morphological resemblance to several species found in Borneo and the Malay Peninsula, namely T. chrysops Ridley (1895: 323) , T. inconspicua Sochor & Dančák in Sochor et al. (2017: 264), T. kinabaluensis T. Nishioka & Suetsugu in Nishioka et al. (2018: 174) and T. malayana Siti-Munirah, Hardy-Adrian, Mohamad-Shafiq & Irwan-Syah in Siti-Munirah et al. (2024: 230). Thismia inconspicua from Borneo and T. malayana from the Malay Peninsula are also genetically related to T. velaris . These three species form a distinct clade among the other Thismia sect. Thismia subsect. Odoardoa species ( Fig. 5 View FIGURE 5 ). Morphologically, all the five above mentioned species share a distorted floral tube that is bent and displaced from the ovary axis. Apart from the more common morphotype of T. velaris with ventricose floral tube ( Fig. 1A View FIGURE 1 ), in some individuals, the floral tube is shifted from the ovary axis, resembling the bent and displaced floral tube seen in the aforementioned species ( Fig. 1B View FIGURE 1 ). This variability suggests that floral tube shape alone may not suffice to distinguish T. velaris from these species. The structure of the connectives, however, provides a clear distinction. Thisimia chrysops , T. inconspicua , T. kinabaluensis and T. malayana , are characterized by a supraconnective with two claviform appendages, which are absent in T. velaris . In addition, T. velaris features a uniquely shaped lateral stamen appendage, which is elongated in the middle, hanging downward in the form of a translucent rectangular veil. This structure has not been documented in any other Thismia species.